I think the most remarkable part of my basement garden was that I did not put all that much effort into it. I got a Lithonia "high bay" 400 HPS fixture, reasoning that the reflector on a lamp made to be mounted high would focus the light in a smaller area. I just put a cord on it and hung it from a chain.
Except for the lamp, it is just like growing plants in pots outside, except there are 90% less insects and no hungry critters to snack on your crops.
I did some experiments with adjusting the lamp timer and long days didn't keep my beans from producing. Some plants want "seasons" but mine didn't seem to mind.
Now I have a wife, and a basement again, and we are both interested in starting a small "farm." LEDs are viable now and I want to look into this.
"Space buckets" are probably the smallest scale you can easily do. With the red/blue grow LEDs you can get more usable light from a solar panel than straight sunlight can provide.
I've been looking for a change from outdoor gardening and a high density 1 m^2 indoor plot with 100W red/blue LED + 100W panel + automatic watering system sounds like a fun combination. Plus I can finally try growing tropical fruit and vegetables.
I guess I messed up the math the first time around because I'm getting something different this time.
* 45% of sunlight is in the photosynthetically active wavelength range
* Solar cells are 20% efficient
* Red LEDs are 39% efficient and blue LEDs are 35% efficient
So no, I was kind of off base there. Straight sunlight is still 6x more energy for plants. But it is close! 40% efficient panels exist and my LEDs efficiency numbers were from 2012 so the gap might be smaller. If you do this calculation yourself, remember to ignore lumens. They are a human perceptual unit and are completely meaningless for plants.
Now for human-visible light it is a little different. With the most efficient solar cells and white LEDs we can do better than the sun. (Straight sunlight is 93 lumens per watt. A 40% solar cell and 250 lumen/watt LED outperforms the sun.) Maybe this is what I was thinking of.
